Electrical measuring device



Nov. 17, 1936.

w. J. BULLARD ELECTRICAL MEASURING DEVICE Filed Nov. 24, 1955 .m mzzjPatented Novc 17, 1936 'uirEo A STATES PATENT OFFICE ELECTRICALMEASUBING DEVICE o William J. BullardQWest Orange, N. .L, assignor toWestern Electric Company,

Incorporated,

New York, N. Y., a corporation of New York Application November 24,1933, Serial No. 699,482

8 Claims.

This invention relates to an electrical measuring device, and moreparticularly to a device for measuring resistance.

An object of the invention is to provide a simple, efficient, andpractical device for measuring theresistance of electrical articles andapparatus.

In accordance with the object, one embodiment of the invention comprisesthree polarized relays having sets of magnetically balanced coils, oneset of the coils including one coil of each relay being included in acircuit with an article, the resistance of which is to be measured,another set-of the coils being included in a circuit with a variableknown resistance, while the coils of the other set are in a commoncircuit and electrically bias the armatures of the relays against theirback contacts, the front contacts thereof being disposed in indicatinglamp circuits so that difierent indications will be given if the articleunder test contains the correct amount of resistance or if theresistance thereof is too high or too low.

Other objects and advantages will be apparent from the followingdetailed description taken in conjunction with the accompanying drawing,

wherein I Fig. 1 is a wiringdiagram illustrating one form of theinvention, and

Fig. 2 is a wiring diagramillustrating another form of the invention.

Referring now to Fig. 1 of the drawing, there are shown polarized relaysill, ii and i2 having permanent magnets i3, it and 55, respectively, thenorth and south poles of which are respectively indicated by letters Nand S. Armatures it, it and it are pivotally secured at their "inner orlower ends to their respective magnets 83, it and 55, while their outeror free ends are positioned to engage the back contacts 2t, 2t and 22,respectively,'or front contacts 23, 2d and 25,

respectively. 'I'he'front contact 25 is connected to the armature itthrough a conductor 30 and the back contact 2!! is connected to thearmature it through a conductor 3!. The front contact 24 is connected toone side of an indicating lamp 32, the other side of the indicating lampbeing connected to a grounded battery 353. The back contact 22 isconnected to one side of an indicating lamp 35 through a conductor 35;,while the other side of the indicating lamp is connected tov the 5()battery 33 through aconductor ill. The front contact 25 is connected toone side of an indicating lamp it through a conductor 35 while the otherside of the indicating lamp is connected to the battery The armature itis connected to ground through a conductor ii. completes 55, theconductor 55 to ground.

the indicating circuit which will be described more in detailhereinafter.

Around the armatures l6, "and it are disposed three sets of coils, oneset of which is in a. test circuit including an unknown resistance of 6an article, the resistance of which is to be measured, another set beingin a circuit including a known resistance and the third set being in acircuit which may be termed a biasing circuit.

The first or test circuit includes coils 45, 46 and 10 41, whichcircuitmay be completed from a grounded battery .48 through a conductor 49, anunknown resistance 55, such as an apparatus or an article beingmeasured, a conductor 5|, the coil 45, a conductor 52, the coil 45, aconductor 53, 15 the coil 41, a conductor 54 through a switch 55 whenclosed, a conductor 55 to ground.

The second or known resistance circuit includes coils 60, BI and 62,which circuit may be completed from a grounded battery 55, through a 20conductor 65, a variable resistance 61, a conductor 68, the coil 69, aconductor 59, the coil 66, a conductor lil,'the coil 52, a conductor 1l, the conductor 54, the switch 55, the conductor 56 to ground. 25

'The third or biasing circuit, which includes coils l5, l6 and I1, maybe completed from grounded battery 65 through the conductor 65, a knownfixed resistance til, a conductor ill, the coil 15, a conductor 82, thecoil it, a conductor 83, the coil 30 ll, a conductor 84, the conductor54, the switch Thecoils t5 and it of the relay l2 and the coils and BIof the relay II are parallel wound giving an extremely close inductiveand resistive 35 balance between the two windings of each relay and. areso arranged that the coils of each relay will oppose each other so thatif the current flow through each circuit containing these coils is thesame the resultant magnetic force due to M these coils will be zero.Furthermore, the coils 45 and 5B are so connected that the magnetic fluxcaused by current flow through these coils will tend to convert theupper ends of their armatures into south pole magnets whereas the 45coils 45 and iii are so connected that the magnetic flux caused bycurrent flow through these coils will tend to convert the upper ends oftheir respective armatures into north pole magnets. Therefore, as willbe described more in detail hereinafter, the armatures ii and it may becontrolled by the unbalancing of the set of coils 46 and ti and the setof coils i5 and Gil.

The coils ii and til are so arranged that they will aid instead ofoppose each other to convert gag the upper end of the armature I8 into anorth pole magnet when current passes through these coils. The coils 15,18 and 11 of the biasing circuit are so arranged upon their respectivearmatures as to cause the upper ends thereof to be south pole magnets soas to be attracted by the north pole of their respective permanentmagnets and thus normally bias the armatures against their respectiveback contacts. The purpose of the resistance 80 in the biasing circuitis to decrease current flow through the biasing coils 15, 18 and 11 to aminimum, so

that there will be present a sufficient magnetic force to cause thearmatures to be held against circuit, and the biasing circuit. As soonas these circuits are completed, the magnetic force of the coils 41 and82 will convert the upper end of the armature I8 into a-north poleovercoming the magnetic force of the coil 11, thus causing the armatureI8 to be attracted by the south pole of the magnet I3 where the armaturewill engage its front contact- 23 completing a circuit from groundedbattery 33 through the conductor 34, the. conductor 31, the indicatinglamp 35, the conductor 38, the back contact 22, the armature I8, theconductor 3|, the back contact 2|, the armature I1, the conductor 30,the front contact 23, the armature I8, the conductor 4I to ground. Whenthis circuit is completed the indicating lamp 35, which may be termedan. O. K. lamp, is illuminated indicating that the resistance 50 issubstantially equal to the resistance 61 if this be the case.Furthermore, during every test the armature I8 will be moved intoengagement with its front contact 23, but variations in the resistances50 and 81 will move either the armature I1 or the armature I8 intoengagement with their respective front contacts, breaking the circuit tothe O. K. lamp 35 and completing a circuit to the high indicating lamp32, or the low indicating lamp 38. As for example, let it be assumedthat the resistance 50 is higher or greater than the resistance 81. If

such is the case, the current flow through the test circuit, whichincludes the resistance 50 with the coils 45 and 48, will be less thanthe current flow through the known resistance circuit, which includesthe coils 60 and GI. The magnetic force of the coil 80 will therefore begreater than the magnetic force of the coil 45, thus aiding the biasingcoil in holding the armature I8 against its back contact 22, whereas themagnetic force created by the current flow through the coil 8|, will begreater than the magnetic force of the coil 46 and the biasing coil 18,thus converting the upper end of the armature I1 into a north polemagnet which will be attracted toward the south pole of the perslightlydifferent from that shown in Fig. 1.

the resistance 50 is higher than the resistance into a north pole atwhich time it will be attracted toward the south pole of the permanentmagnet I5 and'into engagement with its front contact 25, completing acircuit through the indicating lamp 38. The armature I1 will retain itsnormal position in engagement with its back contact 2I as the magneticforce of the coil 48 which is greater than the magnetic force of thecoil 81 will aid the biasing coil 18.

The form of the invention shown in Fig. 2 is In this form of theinvention only one polarized relay is used, this relay indicatedgenerally at I00. The relay I comprises a permanent magnet IOI having anorth and south pole respectively indicated by letters N and "S". Anarmature I02 is-pivoted at I03 which is its lower or inner end, thearmature being biased by springs I04 and I05 to centrally position itbetween the poles of the permanent magnet IOI. Around the armature I02are disposed coils I08 and I01, the coil I08 being in a circuit with acoil I08 of a relay I09 the core of. which is indicated at I I0. Thiscircuit may be completed from a grounded battery II2 through a conductorII3 an unknown resistance II4 which may be an electrical device orapparatus, the resistance of which is to be measured, a conductor II5,the coil I08, a conductor II8, the coil I08, a conductor H1, a conductorII8, a switch II9, a conductor I20 to ground. The coil I01 is in acircuit with another coil I25 of the relay I09 which circuit may becompleted from the grounded battery I I2 through the conductor II3, aconductor I26, a variable resistance I 21, a conductor I28, the coilI01, a conductor I29, the coil I25, the conductor II8, the switch II9when closed, the conductor I20 to ground.

An armature I3I of the relay I09 is grounded at I32 and is biased bymeans oi a spring I33 against a stop I34. An indicating circuit includesindicating lamps I38, I31 and I38. A front contact I40 for the armatureI3I is connected to one side of the indicating lamp I38 through aconductor Hi, the other side of the indicating lamp being connected to agrounded battery I42 through a conductor I43. A back contact I44 for thearmature I02 is connected to one side of the indicating lamp I31 througha conductor I45, the other side of the indicating lamp being connectedto the conductor I43 through a conductor I48. A front contact I41 forthe armature I02 is connected to the indi eating lamp I38 through aconductor I48 the other side of the indicating lamp being connected tothe conductor I43 through a conductor I49. The armature I02 which is apart of the indilcaating circuit Just described is grounded at 5 Whentesting the resistance of the article II4- which is properly connectedin the circuit with the coils I08 and I08, the switch H8 is closedcompleting the two circuits containing the "resistance H4 and theresistance I21, the resistance I21 being set at a'predetermined amount.The coils I08 and I01 .areso arranged upon the armature I02 that themagnetic forces thereof when energized will oppose each other, whereasthe 'colls- I08 and I25 of the relay 19 are so positioned that they willaid each other. Therefore, when the switch H9 is closed the armature i3lwill be drawn into engagement with its iront contact i lll completing acircuit through, the indicating lamp I35. If the resistance lid is equalto the resistance I21, the coils tilt and it'll will balance in opposingmagnetic forces and the armature Hi2 will not be moved from its normalposition. However,

if the resistance Md should be greater than the resistance Hi, therewill be a greater current iiow through the coil iill causing a greatermagnetic force from the coil ic'l than the coil its the result of whichwill polarize the armature ,so that it will be attracted to the northpole of the permanent magnet it! movingthe armature into engagement withits back contact Md and completing a circuit from the grounded batterythrough the conductors its and Mt, the indicating lamp ltl, theconductor M5, the back contact M6, the armature m2 to ground ltd. If theresistance lid is lower than the resistance iii, there will be a greaterflow of current through the coil ltd than through the coil it?polarizing the armature N32 to be attracted toward the south pole of thepermanent magnet iill and into engagement with the front contact Mil tocomplete a circuit through the indicating lamp i338. Therefore, when aresistance Hi l is not equal to the resistance i271, either theindicating lamp i317 or the indicating lamp I138 will be illuminated inaddition to the indicating lamp ltt. To determine the amount ofvariation in resistance, the variable resistance may be adjusted untilwhichever indicating lamp it'll or its is illuminated ceases to be so.

In the foregoing description of the two forms of the invention theunknown resistance which is being measured has been described as anarticle, but either form of the invention may be employed to test theresistance of circuits or various electrical apparatus without departingfrom the spirit and scope of the present invention. It is obvious alsothat the principle of the apparatus is not limited to use for comparingelectrical impedances comprising merely resistance.

What is claimed is: i

1. In an electrical measuring device, a plurality of indicatingelements, an electrical circuit including an object the resistance ofwhich is to be measured, a second circuit including a known resistance,each circuit being supplied with an equal electromotive force, a relayactuated by the current flow through one of said circuits for actuatingone of said indicating elements if the resistive force of the object andthe known resistance are equal, and means actuated by a difference inthe electrical current through the circuits caused by a variation inresistive force of the object and the known resistance for selectivelyactuating others of said indicating elements.

2. In an electrical measuring device, a plurality oi relays one of whichis polarized, an electrical circuit comprising an unknown resistance anda cell for each relay, a second electrical circuit comprising a knownresistance and a coil for each relay, the magnetic force of the coils ofsaid polarized relay opposing each other while the magnetic force of thecoils of the other relay aid each other, armatures, tor said v relayscontrolled by the magnetic force of said ity of relays, an electricalcircuit including an unknown resistance and a coil for each relay, asecond electrical circuit including a known resistance and a coil foreach relay, armatures for said relays, a plurality of indicating devicescontrolled by said armatures, a third circuit including a knownresistance and a coil for each relay, said last mentioned coils biasingsaid armatures in a predetermined direction when energized, the coils ofthe first and second mentioned circuits for certain of the relaysopposing each other, and so arranged that certain oi the armatures willbe actuated when there exists a variation in resistiveuforce of theunknown resistance and the first mentioned known resistance toselectively actuate one of said indicating devices.

4. In an electrical measuring device, a relay having an armature and twocoils opposing each other when energized, a circuit'including an unknownresistance and one of said coils, a second circuitincluding a knownresistance and the other coil, each circuit being supplied with an equalelectromotive force, a plurality .of indicating devices and a relayhaving a coil disposed in one of said circuits for energizing one orsaid ina difference in resistance or said resistances varying thecurrent flow through said coils, resulting in the actuation of thearmature of said first mentioned relay to render ineffective the firstmentioned indicating device and energizing one of the other indicatingdevices.

5. In an electrical measuring device, a relay having an armature and twocoils opposing each other when energized, a circuit including an unknownresistance and one of said coils, a second circuit including a variableknown resistance and the other coil, each circuit being supplied with anequal electromotive force, a plurality of indicating devices and a relayhaving a coil disposed in one of said circuits for energizing one ofsaid indicating devices, a difierence in resistance of said resistancesvarying the current flow through the coils of. said first mentionedrelay, resulting in the actuation of the armature to energize one oftheoth-er indicating devices and means for adjusting the variable knownresistance until said second mentioned indicating device is dc-energizedto measure the variation in resistance of said unknown resistance from adesired value.

' 6. In an electrical measuring apparatus, a circuit having means forconnecting therein a known resistance, a circuit having means forconnecting therein an unknown resistance, means for supplying currentto-said circuits, devices for indi-' cating respectively when theunknown resistance has a value bearing a desired relation to the knownresistance, when its value is above said desired value and when itsvalue is below said desired value, and means responsive to the currentsin said circuits for selectively actuating said indicating devices, saidcurrent responsive means comprising polarized relay means havingwindings in said circuits and being normally biased in a direction tocause the actuation of said first mentioned indicating device.

7. In a device for measuring the resistancei'ot an object, a pluralityof relays, an electrical cir cuit arranged to include an object to bemeasured and a coil for each relay, a second electrical circuitcomprising a known resistance and 75 a coil for each relay, armaturesfor said relays actuated by the magnetic force of said coils, and

indicating devices controlled by said armatures, the coils of saidrelays being so arranged that variation in resistance between the objectand the known resistance will selectively actuate one of the armatures.

8. In a device for measuring the resistance oi. an object, a pluralityof relays, an electrical circuit arranged to include an object to bemeasured and a coil for each relay a second electrical circuitcomprising a known resistance and a coil for each relay, armatures Iorsaid relays actuated by the magnetic force of said coils, and indicatingdevices controlled by said annatures, the coils of each of said relaysbeing so arranged that their magnetic forces will balance when theresistances I are equal and the armatures will be selectively actuatedto energize one 01 the indicating devices when theresistances vary.

WILLIAM J. BULLARD.

